1. Field of the Invention
The present invention provides a process for preparing composite articles comprising vulcanizing at least one rigid component based on a thermoplastic polyester with at least one flexible component which is a vulcanizate. The invention further provides such composite articles.
2. Discussion of the Background
Articles made from a single material often lack a variety of desirable properties. For example, articles made from a single material can not possess high strength and rubber elasticity or high hardness and rigidity on one side while simultaneously possessing non-skid properties on the other side.
To provide articles with multiple properties, composite articles manufactured from different materials are used. Composite articles require firm adhesion between the different materials in order to function properly. Various methods of firmly bonding rubbers and thermoplastics to one another are known. Composite materials of thermoplastically rigid and elastomeric molding compositions are usually joined together by gluing, screwing, riveting, mechanical clawing, or using an adhesion promoter. Unfortunately, to date these methods have provided composite articles in which the different materials are unsatisfactorily bonded.
More recently, processes have been developed for production of molding compositions based on polyphenylene ethers (PPE) bonded to certain rubbers which can be vulcanized with sulphur or peroxide (compare EP-A-0 196 407 and EP-A-0 315 749). The adhesive strength values achieved by these processes are considerably improved.
It would be desirable to prepare other composite materials in which the thermoplastic component simultaneously has a good resistance to solvents, stability during weathering and excellent sliding friction properties, in addition to a high heat distortion point. For example, it would be desirable to replace the PPEs in the above composites with other thermoplastics such as polyesters which are known to meet the above-mentioned requirements. Unfortunately, PPE can not be directly replaced with polyesters because adequate adhesion values cannot be achieved under the process conditions recognized as essential (see comparison experiments).
Other methods are known for preparing composites of polyesters and rubbers. EP-A-0 375 867 describes a process for the preparation of such composites in which the thermoplastic content comprises, to the extent of at least 30%, a reaction product of a thermoplastic polyester and a polyisocyanate. These reaction products have the disadvantage that, at a sufficiently high concentration of polyisocyanate, they can be injection-molded or extruded only in a very narrow processing window.